Embodiments of the present invention relate to a thin film transistor-liquid crystal display array substrate and a manufacturing method thereof.
Thin film transistor liquid crystal displays (TFT-LCDs) possess advantages of small volume, low power consumption, low radiation, etc., and are gradually prevailing in the market of flat plate displays. As for a TFT-LCD, an array substrate and the manufacturing method thereof dominate to a large extent performance, yield, and price of the final products.
In order to efficiently reduce the production cost of TFT-LCDs and improve yield, the manufacturing process of a TFT-LCD array substrate is gradually simplified. Such manufacturing process has been evolving from an initial 7-mask process to a current 4-mask process based on half tone or gray tone photolithography technology. Besides, a 3-Mask process is under research and development.
One 3-Mask process has been proposed in Chinese patent application CN 200510132423.X, in which a gate line and a gate electrode are formed through a patterning process with a first normal mask; a data line, a source electrode, a drain electrode, and a thin film transistor (TFT) channel region are then formed through a patterning process with a second gray-tone mask; and a pixel electrode is finally formed through a patterning process with a third normal mask. In this method, the third patterning process forms a transparent pixel electrode directly contacting with the surface of the drain electrode in a common manner, the sidewalls of the photoresist pattern that is subject to exposure and development have a vertical shape after photolithography, and the sidewalls of the passivation layer have an inwardly concaved shape with over-etching during etching process, so that the transparent conductive thin film to be deposited subsequently is disconnected at the sidewalls of the passivation layer. However, in practice, such a process requires applying a relatively thick photoresist layer to make the slope of the photoresist edge as steep as possible and close to 90 degree. Unfortunately, such measure practically cannot appropriately disconnect the transparent conductive thin film at the photoresist edges. In this case, the cost increases, and the quality of a lift-off process cannot be ensured. As for the TFT-LCD array substrate in preparation, any adhesion of the transparent conductive thin film results in residual, which brings great harm to the lift-off process and gives rise to defects to be overcome of the 3-Mask process.